Jimmy Savile would regularly take teenage girls to a private hospital block alone, a former porter has claimed.

Terry Pratt said the late Jim'll Fix It star was regularly handed a key to the nurses' accommodation building at Leeds General Infirmary during the late 1980s. The ex-worker told the BBC that Savile would arrive with the girls in the early hours of the morning and then leave before dawn.

Scotland Yard has launched an investigation into the television and radio star's activities, and he is now believed to have been one of the UK's most prolific abusers, with about 300 possible victims.

Mr Pratt said he became suspicious when Savile began arriving in the middle of the night with different girls who seemed "star-struck" and were "not streetwise". He added that the celebrity, who was a volunteer and fundraiser for the hospital, would make several late-night visits a month where he would ask for the key to the accommodation block, spend a few hours there and then leave at 5am.

Leeds Teaching Hospitals NHS Trust said it was "shocked" by the claims surrounding Leeds General Infirmary and has vowed to help the Metropolitan Police with inquiries into the alleged abuse.

A spokesman for the trust said: "We continue to be shocked by each new allegation. It is important that they are investigated properly. Once again we urge anybody who has any concerns to contact us so that we can pass information on to the police or to contact the police directly via the NSPCC helpline, 0808 800 5000."

Detectives are following 400 lines of inquiry as part of the investigation while the BBC has launched an inquiry into the culture and practices at the corporation in the era of Savile's alleged sexual abuse. It is also looking at the decision-making process that saw a Newsnight investigation into Savile's activities shelved.

Deputy Prime Minister Nick Clegg has said "heads will need to roll" at the BBC if it is discovered that abuse was ignored.

Earlier this week it emerged that Savile was barred from any involvement with the BBC's Children In Need charity. Sir Roger Jones, a former chairman of the charity, said he had been uncomfortable about allowing Savile to have any association with their work. Although he had "no evidence" that Savile was up to anything, he said he behaved strangely, adding: "I think we all recognised he was a pretty creepy sort of character."